EP4283331A1 - Détection optique et mesure de distance - Google Patents

Détection optique et mesure de distance Download PDF

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Publication number
EP4283331A1
EP4283331A1 EP22175234.8A EP22175234A EP4283331A1 EP 4283331 A1 EP4283331 A1 EP 4283331A1 EP 22175234 A EP22175234 A EP 22175234A EP 4283331 A1 EP4283331 A1 EP 4283331A1
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EP
European Patent Office
Prior art keywords
light
signal
threshold
sensor
pulse
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP22175234.8A
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German (de)
English (en)
Inventor
Martin Marra
Christoph Michalski
Klaus Clemens
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Sick AG
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Sick AG
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Publication date
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Priority to EP22175234.8A priority Critical patent/EP4283331A1/fr
Publication of EP4283331A1 publication Critical patent/EP4283331A1/fr
Pending legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/487—Extracting wanted echo signals, e.g. pulse detection
    • G01S7/4873—Extracting wanted echo signals, e.g. pulse detection by deriving and controlling a threshold value
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/02—Systems using the reflection of electromagnetic waves other than radio waves
    • G01S17/06—Systems determining position data of a target
    • G01S17/42—Simultaneous measurement of distance and other co-ordinates
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/88—Lidar systems specially adapted for specific applications
    • G01S17/93—Lidar systems specially adapted for specific applications for anti-collision purposes
    • G01S17/931—Lidar systems specially adapted for specific applications for anti-collision purposes of land vehicles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
    • G01S7/483—Details of pulse systems
    • G01S7/486—Receivers
    • G01S7/487—Extracting wanted echo signals, e.g. pulse detection
    • G01S7/4876—Extracting wanted echo signals, e.g. pulse detection by removing unwanted signals

Definitions

  • the invention relates to a distance-measuring optoelectronic sensor and a method for optical detection and distance measurement of an object in a surveillance area according to the preamble of claim 1 or 15.
  • the transit time of a light signal is often measured, which corresponds to the distance via the speed of light.
  • a light beam is emitted into the monitoring area and the light beam reflected by objects is received again in order to then evaluate the received signal electronically.
  • a pulse-based method direct ToF, Time of Flight
  • light pulses are emitted and their transit time until the returning light pulse is received is determined.
  • pulse averaging process as an extension of a single pulse process, for example in the EP 1 972 961 A2 is presented, pulses are repeatedly sent and received in order to build up a histogram and then evaluate the histogram.
  • a periodic transmission pattern is modulated in a phase method (iToF, indirect ToF) and the receiving phase is determined.
  • the scanning beam can be moved, as happens in a laser scanner.
  • a light beam generated by a laser periodically sweeps over the monitoring area with the help of a deflection unit.
  • the angular position of the object is deduced from the angular position of the deflection unit, and thus the location of an object in the monitoring area is recorded in two-dimensional polar coordinates.
  • Another way to extend the measuring range is to simultaneously record several measuring points with several scanning beams. This can also be combined with a laser scanner, which then not only records one surveillance level, but also across one Numerous monitoring levels cover a three-dimensional spatial area. In most laser scanners the scanning movement is achieved by a rotating mirror. Especially when using multiple scanning beams, it is also known in the prior art to instead rotate the entire measuring head with light transmitters and light receivers.
  • a multi-layer scanner is used, for example EP 3 518 000 A1 described.
  • the detection sensitivity of simple photodiodes is not sufficient in many applications.
  • an avalanche photodiode Avalanche Photo Diode
  • the incident light triggers a controlled avalanche breakdown (avalanche effect).
  • the charge carriers generated by incident photons are multiplied, and a photocurrent is created that is proportional to the intensity of the light received, but is significantly larger than with a simple PIN diode.
  • the avalanche photodiode is biased above the breakdown voltage, so that even a single charge carrier released by a single photon can trigger an avalanche, which then recruits all available charge carriers due to the high field strength.
  • the avalanche photodiode like the Geiger counter that gives it its name, counts individual events.
  • Avalanche photodiodes in Geiger mode are also called SPAD (Single-Photon Avalanche Diode).
  • Geiger APDS or SPADs are very fast, highly sensitive semiconductor-based photodiodes.
  • a disadvantage of the high sensitivity is that not only a useful light photon, but also a weak disturbance event caused by extraneous light, optical crosstalk or dark noise can trigger the avalanche breakthrough. This disruptive event then contributes to the measurement result with the same relatively strong signal as the useful light received and cannot be distinguished from it even in the signal.
  • the avalanche photodiode then remains insensitive for a dead time of approx. 5 to 100 ns and is no longer suitable for further measurements. It is therefore common practice to connect several SPADs together and evaluate them statistically.
  • a name for a light receiver with several SPADs connected together to output a sum signal is SiPM (Silicon Photo Multiplier), whereby silicon is only the common, but not the only, underlying semiconductor.
  • the DE 20 2013 101 039 U1 activates its avalanche photodiode elements only in a time window after emitting transmitted light that corresponds to a distance range around an expected object distance. This completely hides the close range of an object that is expected to be further away, but does not help in distinguishing between disturbances and an object that is expected to be close.
  • the sensitivity of the light receiver is dynamically adjusted to an expected distance of the object.
  • the EP 3 770 633 B1 deals with an optoelectronic sensor for distance determination using a time-of-flight method that has two scanning units with a low and a high threshold respectively.
  • the high threshold serves as a kind of filter as to whether the samples with the low threshold are further evaluated.
  • threshold adjustments are provided by means of diodes, which determine the noise level approximately as the square root of a direct current component of the received signal.
  • the as yet unpublished European patent application with the file number 22164402.4 In addition to a light transit time, measures the level of the received signal and thus adjusts a threshold for determining a reception time. However, all of these threshold adjustments are not made to address the problem of close-range interference.
  • the sensor has a light transmitter, a light receiver with at least one light receiving element and a control and evaluation unit to send out a light signal to receive and to measure the light transit time and thus the distance to an object by evaluating the received signal.
  • the received signal is compared with a threshold signal and thus evaluated with a threshold.
  • the time of reception is found directly or indirectly via the threshold signal. Immediate means, for example, that a received pulse is recognized by exceeding the threshold and is thus localized in time.
  • the threshold is then a detection threshold. Indirectly, the threshold serves to digitize or binarize the received signal, with further digital evaluation then finding the time of reception.
  • the threshold is a comparator threshold.
  • the light signal emitted is preferably a pulse.
  • the at least one light-receiving element preferably a plurality of light-receiving elements or cells, can in principle be an APD or another light detector. It is preferably a light receiving element operated in Geiger mode, i.e. a SPAD-based light receiver. In particular, the photocurrents of several such light receiving elements are combined with one another early in the processing chain.
  • An example is an implementation as a silicon photomultiplier (SiPM), which represents a quasi-analog component.
  • the invention is based on the basic idea of using a less sensitive threshold in a close range.
  • the spatial close range can be assigned to a temporal initial phase of the distance measurement via the light travel time.
  • this initial phase begins with the emission of the light signal at a light travel time of zero or an object distance of zero.
  • a time delay be it negative, in order to achieve a steady state of the adapted threshold state at the time the light signal is emitted, or positive, in order to give the close range a certain minimum distance from the sensor.
  • the threshold, according to the invention which is less sensitive during the initial phase, is usually set higher than during the rest of the distance measurement. Since there may be embodiments with inverted signals (active-low) and the threshold must then be reduced to make it less sensitive, it is more generally referred to as adjusting the threshold signal.
  • the invention has the advantage that incorrect measurements due to disturbances such as fog or spray are avoided or at least reduced by means of threshold adjustment in the close range. This is accompanied by a certain loss of sensitivity for objects with weak remission at close range.
  • the interference suppression and the sensitivity can be balanced against each other by the extent of the threshold adjustment.
  • only an electronic control is required to design the threshold adjustment differently, or in an analog-electronic design, a simple re-dimensioning of the analog components can be carried out.
  • Fog and spray are just examples of disruptive effects in the close range that can be hidden according to the invention.
  • other effects such as optical crosstalk, for example due to windshield reflections, particularly due to dirt or dust particles, fog or liquid, can be suppressed.
  • the control and evaluation unit preferably has a digitization unit or binarization unit, with the threshold signal setting a digitization threshold or binarization threshold.
  • the threshold adjusted in the initial phase is used to digitize the received signal.
  • the threshold is then also referred to as the comparator threshold. It differentiates between background and useful light, and in particular recognizes a received pulse using a reception signal above the threshold. A less sensitive threshold therefore only detects particularly pronounced useful light, which prevails even against the increased background in the close range under disturbing conditions such as fog or spray.
  • multiple thresholds are used for additional digital states.
  • a less sensitive threshold means that higher digital values are only assumed for pronounced useful light.
  • the threshold signal can alternatively be used directly to determine the time of reception instead of indirectly as in this embodiment. The exceeding of the threshold then directly localizes a received pulse in time, if necessary with corrections.
  • the control and evaluation unit is preferably designed to send out and receive a light signal in a large number of individual measurements, to build a histogram from the respective received signals of the individual measurements by comparing the received signal with the threshold signal and to evaluate the histogram to determine the time of reception .
  • measurements are carried out using a pulse averaging method, for example in the mentioned in the introduction EP 1 972 961 A2 is described.
  • the threshold is preferably a comparator threshold or binarization threshold.
  • the histogram collects the number of individual measurements in which the binarization threshold is exceeded in the respective time bins as events in time bins. This results in a kind of zero line with an average, namely a number of events, how often the threshold is exceeded without receiving the remitted light signal.
  • the less sensitive threshold in the initial phase ensures fewer events and lowers this average.
  • a pulse averaging method a single pulse method remains conceivable.
  • the control and evaluation unit is preferably designed to generate an analog threshold signal and compare it analogously with the received signal.
  • the threshold comparison therefore still takes place in the analog processing stage of the received signal.
  • Very simple circuits are possible for this.
  • a differentiation between disturbances and objects in the close range is carried out using algorithms after digitization, and the digitized received signals are usually processed using complex algorithms. This is therefore a completely different approach than an analogue threshold.
  • the control and evaluation unit preferably has a comparator with a first input and a second input, the received signal being applied to the first input and the threshold signal being applied to the second input.
  • the comparator is a very simple analog component used to evaluate the threshold.
  • the received signal is preferably binarized using the comparator.
  • the threshold signal sets the comparator threshold or binarization threshold for this purpose.
  • the control and evaluation unit is preferably designed to generate an adaptation pulse that changes the threshold signal in the initial phase.
  • the threshold signal is adjusted in a pulse-like manner.
  • the course of the threshold signal required for the initial phase is specified by the adaptation pulse. Outside the initial phase, the threshold signal is preferably constant.
  • the control and evaluation unit is preferably designed to generate the adaptation pulse with a pulse characteristic in start, end, duration, rise behavior and/or decay behavior in accordance with a predetermined adaptation of the threshold signal.
  • the adaptation pulse and thus the behavior of the threshold in the initial phase can be parameterized as desired using the pulse characteristics.
  • the control and evaluation unit is preferably designed to generate a trigger pulse that is at a known time offset from the emission of the light signal, in particular triggers the emission.
  • the trigger pulse is an electrical signal that is converted directly or indirectly in the light transmitter with a known time reference into the emitted light signal.
  • the sensor can be synchronized via the trigger pulse, so the timing of the initial phase is known.
  • the control and evaluation unit is preferably designed to generate the adaptation pulse from the trigger pulse in an adaptation pulse generation unit.
  • the trigger pulse is also responsible for generating the adaptation pulse. Synchronization is thus ensured via the trigger pulse, and the initial phase with an adapted threshold signal is therefore bound to the optical light signal, possibly with a desired, known time offset.
  • An adaptation pulse generation unit can in particular be designed as an analog adaptation circuit that converts the incoming trigger pulse into an adaptation pulse. The dimensioning of the switching elements of the adaptation circuit determines the pulse characteristics of the adaptation pulse.
  • the adaptation pulse generation unit preferably has a capacitor which is charged by the trigger pulse and discharges while generating the adaptation pulse.
  • the capacitor is a very simple electrical component, but it already provides a significant part of the desired conversion of the trigger pulse into the adaptation pulse.
  • the capacitance of the capacitor influences the pulse characteristics.
  • the adaptation pulse generation unit preferably has a first resistor and a diode, in particular a Schottky diode, for charging the capacitor.
  • the adaptation pulse generation unit preferably has a divider circuit with a second resistor and a third resistor for discharging the capacitor.
  • the amplitude of the adaptation pulse can be influenced via the divider circuit or the ratio of the second resistor to the third resistor.
  • the second resistor and third resistor determine the discharge time constant with the capacitance of the capacitor.
  • the adaptation pulse generation unit is preferably designed to generate a negatively directed adaptation pulse.
  • the threshold signal is usually at zero in the resting state, so a higher threshold is less sensitive, so a positive adaptation pulse is required for the corresponding adaptation.
  • a negative initial pulse is required for a less sensitive threshold. This is also possible in a simple analog matching circuit. For example, a capacitor is charged in the idle state and discharged for the initial phase by a negative trigger pulse, whereby a negative adjustment pulse can then be tapped.
  • the control and evaluation unit is preferably designed to selectively switch the adjustment of the threshold signal on or off in the initial phase. This means that there is a type of selectable fog or interference mode in the sensor for the threshold adjustment according to the invention in the close range. This mode can also be switched off; the sensor is then operated without the threshold adjustment in the initial phase, for example for indoor operation or depending on the weather if no disruptions are expected.
  • the sensor is preferably designed as a laser scanner, in particular as a multi-layer scanner, and has a movable deflection unit with the help of which the light signals are periodically guided through the monitoring area.
  • the deflection unit is designed in any way, for example as a rotating mirror, but preferably in the form of a rotatable scanning unit, which practically forms a movable measuring head in which the light transmitter and / or the light receiver and preferably also at least parts of the control and evaluation unit are accommodated.
  • a multi-level or multi-layer scanner scans the monitoring area in several layers or approximately planes with the movement of the movable deflection unit.
  • FIG 1 shows a very simplified schematic block diagram of an optoelectronic sensor 10 in an embodiment as a single-beam light sensor.
  • the embodiment as a light button is purely an example.
  • Another embodiment as a laser scanner will be discussed later with reference to Figure 2 explained.
  • several sensors 10 can be connected to one another to form a scanning light grid with several, usually parallel beams, which measures or monitors distances in each beam.
  • This list of optoelectronic sensors in which the invention can be used is not exhaustive. Mobile systems are also conceivable in which the sensor 10 is mounted movably.
  • a light transmitter 12 for example an LED or a laser light source, sends a light signal, preferably a light pulse, into a monitoring area 14. If it hits an object 16 there, part of the light signal is remitted or reflected and returns to a light receiver 18.
  • this light receiver 18 has a plurality of light receiving elements, which are designed as avalanche photodiode elements 20 in Geiger mode or SPADs. It is preferably a SiPM (Silicon Photomultiplier).
  • the avalanche photodiode elements 20 are arranged, for example, in a matrix, a line or in another pattern or irregularly.
  • the light receiver 18 does not have SPADs, but other light receiving elements, or is a single receiver with only one light receiving element.
  • the received signals from the avalanche photodiode elements 20 are read out by a control and evaluation unit 22 and evaluated there.
  • the received signals can be evaluated individually or in groups to obtain a spatial resolution, or combined to form a sum signal. In the following, for the sake of simplicity, only one received signal is often considered as a representative.
  • the control and evaluation unit 22 determines a light transit time from the emission of a light signal to its reception and converts this into a distance using the speed of light.
  • the received signal is evaluated with a threshold, and this threshold is adapted for the detection of an object 16 in the close range under the influence of interference, for example from fog or spray.
  • control and evaluation unit 22 can also act on the light transmitter 12 and/or the light receiver 18, for example to shape and trigger the light signal or to determine its properties, or to set the properties of the light receiver 18.
  • the separation into light receiver 18 and control and evaluation unit 22 in Figure 1 This is also conceivable in practice, but primarily serves as an explanation.
  • these elements are at least partially integrated on a common chip, the surface of which is shared by light-sensitive areas of the avalanche photodiode elements 20 and circuits assigned to individual or groups of avalanche photodiode elements 20 for their evaluation and control.
  • the optical arrangement with a light transmitter 12, which covers a small portion of the light receiver 18, is also pure exemplary.
  • other known optical solutions can be used, such as autocollimation with a beam splitter and common optics, or pupil division, where two separate optics are provided and light transmitters and light receivers are arranged next to each other.
  • FIG 2 shows a schematic sectional view through an optoelectronic sensor 10 in an embodiment as a laser scanner.
  • the same or corresponding features are already included Figure 1 introduced reference numerals, and only deviating properties will be described.
  • the sensor 10 roughly comprises a movable scanning unit 24 and a base unit 26.
  • the scanning unit 24 is the optical measuring head, while the base unit 26 accommodates further elements such as a supply, evaluation electronics, connections and the like.
  • the scanning unit 24 is set into a rotational movement about an axis of rotation 30 with the aid of a drive 28 of the base unit 26 in order to periodically scan the monitoring area 14.
  • Light transmitters 12 and light receivers 18 are accommodated in the scanning unit 24.
  • the light transmitter 12 here has, for example, an LED or a laser in the form of an edge emitter or VCSEL and, with the aid of a transmission optics 32 shown, sends out several transmission light beams 34 with mutual angular offset into the monitoring area 14.
  • the generation of the multiple transmitted light beams 34 is possible, for example, via a large number of light sources and/or through optical elements such as beam splitters, light guides or diffractive elements.
  • the internal light path of the transmitted light beams 34 can be shielded by an opaque tube 36.
  • the remitted light beams 38 are guided by receiving optics 40 onto the light receiver 18.
  • the light receiver 18 has several groups of SPADs (Single-Photon Avalanche Diode) or several SiPMs (Silicon Photomultipliers) in order to capture the several remitted light beams 38.
  • the reception path is preferably designed with the design of the reception optics 40 as well as the arrangement and alignment of the light receiver 18 and the reception optics 40 so that a remitted light beam 38 falls on a specific group of SPADs or a SiPM.
  • interactions are generally not possible for all distances objects to avoid. This may be a reason why the remitted light beams 38 should preferably be received separately in a multiplex operation.
  • the light receiver 18 is arranged on a circuit board 42, which lies on the axis of rotation 30 and is connected to the shaft 44 of the drive 28.
  • the receiving optics 40 is supported by legs 46 on the circuit card 42 and holds another circuit card 48 of the light transmitter 12.
  • the two circuit cards 42, 48 are connected to one another and can also be designed as a common Flexprint circuit card.
  • the in Figure 2 The optical structure shown with two circuit cards 42, 48 or circuit card areas stacked one above the other and a common transmission optics 32 arranged centrally within the receiving optics 40 is to be understood purely as an example.
  • any other arrangement known per se for example from one-dimensional optoelectronic sensors or laser scanners, such as a biaxial arrangement or double eye arrangement or the use of a deflection or beam splitter mirror would be possible.
  • a non-contact supply and data interface 50 connects the movable scanning unit 24 with the stationary base unit 26.
  • the control and evaluation unit 22 is located there, which can also be accommodated at least partially on the circuit board 42 or at another location in the scanning unit 24.
  • the drive 28 is controlled by it and the signal of an angle measuring unit, not shown, which is generally known from laser scanners, is recorded, which determines the respective angular position of the scanning unit 24.
  • two-dimensional polar coordinates of all object points in a scanning plane are available after each scanning period with angle and distance.
  • the respective scanning plane is also known via the identity of the respective remitted light beam 38 and its detection location on the light receiver 18, so that overall a three-dimensional Spatial area is scanned.
  • the object positions or object contours are therefore known and can be output via a sensor interface 52.
  • the sensor interface 52 or another connection, not shown, serves conversely as a parameterization interface.
  • the sensor 10 can also be designed as a safety sensor for use in safety technology to monitor a source of danger, such as a dangerous machine.
  • a protective field is monitored that must not be entered by operating personnel while the machine is in operation. If the sensor 10 detects an inadmissible protective field intervention, such as an operator's leg, it triggers an emergency stop of the machine.
  • Sensors 10 used in safety technology must work particularly reliably and therefore meet high safety requirements, for example the EN13849 standard for machine safety and the EN61496 device standard for non-contact protective devices (BWS).
  • the sensor interface 52 can then be designed as a safe output interface (OSSD, Output Signal Switching Device) in order to output a safety-related switch-off signal in the event of a protective field intervention by an object.
  • OSSD Output Signal Switching Device
  • the sensor 10 shown is a laser scanner with a rotating measuring head, namely the scanning unit 24.
  • periodic deflection using a rotating mirror is also conceivable.
  • a further alternative embodiment pivots the scanning unit 24 back and forth, either instead of the rotational movement or additionally about a second axis perpendicular to the rotational movement, in order to also generate a scanning movement in elevation.
  • a solid-state lidar design is also possible.
  • Figure 3 shows with a solid line an exemplary received signal from the light receiver 18 in the form of a time-dependent voltage signal.
  • the time axis is translated into an object distance via the speed of light, and the voltage is a possible measure of the level of the received signal.
  • an interference peak 54 results, which is generated, for example, by scattering or reflection from fog or spray particles.
  • Object peak 56 generated.
  • the received signal moves to a resting level 58, which is caused by extraneous light and dark noise.
  • the downward oscillation behind the object peak 56 is due to the dead times of SPADs and does not need to be taken into account here.
  • the interference peak 54 would be incorrectly recognized as an object and an object distance would therefore be measured that is much too small.
  • the interference peak is masked out and the actual object peak 56 is used as the basis for the distance measurement.
  • Figure 4 shows similar Figure 3 another exemplary received signal.
  • the interference peak 54 is even more pronounced, for example in denser fog, and therefore also exceeds the adjusted threshold 62.
  • a threshold adjustment in the close range cannot therefore resolve all situations. This problem occurs at the latest when the interference peak 54 becomes as strong as an object peak 56 from a bright or even reflective target or the received signal even saturates in the close range. Rather, by choosing the adapted threshold 62, a trade-off can be made between interference suppression and object sensitivity.
  • the various peaks 54, 56 can be distinguished by further measures, for example based on their sequence on the time axis or their pulse shape. In any case, an adapted threshold 62 makes it possible to deal with disturbances in the short range in many cases.
  • the threshold 60, 62 is used in the example Figures 3 and 4 directly the localization of peaks 54, 56, it can be viewed as a detection threshold.
  • the received signal is digitized and in particular binarized before further evaluation.
  • the threshold is then a comparator threshold for digitization or binarization.
  • a distance measurement is based on a large number of individual measurements in which a light pulse is emitted, received again and a histogram is built up from the received signal evaluated using the comparator threshold.
  • the bins of the histogram count how often the received signal is above the threshold in the time period represented by the respective bin.
  • the peaks 54, 56 are reflected in the bins, so that a reception time can be found by evaluating the histogram.
  • a pulse averaging method is mentioned, for example, in the introduction EP 1 972 961 A2 described, to which reference is made in addition.
  • the binary states can be further differentiated; this is particularly understood here as digitizing.
  • Figure 5 illustrates the effect of adjusting the comparator threshold in an initial phase or in the close range.
  • the average of the counts in the bins of the histogram is plotted here, drawn for simplicity as a continuous line instead of as a discrete bar chart. This is the number of above-threshold events to be expected without disturbances or objects. If the comparator threshold is raised in the initial phase, a stronger received signal is required to generate an event to be counted. Therefore, the initial mean value 64 is lower in the initial phase before a middle position 66 is established after the initial phase. As a result, a disturbance in the close range is weakened, and the downstream histogram evaluation will therefore measure the distance to an object rather than to the disturbance.
  • the adapted detection threshold immediately detects peaks 54, 56, and therefore with a less sensitive threshold only an object peak 56 and no longer an interference peak 54 is detected, at least as long as the interference peak 54 does not assume a strength comparable to the object peak.
  • the adapted comparator threshold according to FIG. 5 causes a kind of attenuation in the initial area of the histogram. The actual determination of the time of reception only follows in the next step, whereby an interference peak in the close range of this histogram is less pronounced, thereby making it easier to identify an object peak.
  • the histogram evaluation could certainly be carried out again with a detection threshold, which this time is set to a minimum count that is expected from an object, whereby this detection threshold itself could be adjusted again in the close range.
  • Figure 6 shows a block diagram to explain the threshold adjustment in the close range.
  • a comparator threshold of a pulse averaging method is adjusted, as just described with reference to Figure 5 explained.
  • a detection threshold could be adjusted in an analogous manner, as described above reference to the Figures 3 and 4 explained, preferably in a single-pulse method in which there is no need to build up and evaluate a histogram.
  • a trigger generation 68 generates a trigger pulse that defines the start of a distance measurement. With a defined time reference to the trigger pulse, the light transmitter 12 emits a light pulse that is reflected back at the object 16. The light receiver 18 converts the incident light into a received signal. The trigger pulse is also supplied to an adaptation pulse generation unit 70. The adaptation pulse emanating there is combined with a threshold signal, for example added to a constant threshold signal. Due to the adaptation pulse, the threshold signal sets a less sensitive threshold in an initial phase of the measurement, which corresponds to a close range.
  • the received signal is then present at one input of a comparator 72 and the threshold signal is present at another input.
  • the comparator 72 preferably works as a binarizer, which assumes one binary state when the received signal is below the threshold and the other binary state when the received signal is above the threshold.
  • a histogram generation unit 74 sorts these binary events into time bins and thus builds up a histogram using repeated individual measurements, each with a light pulse transmitted and received again.
  • a histogram evaluation 76 locates an object peak 56 in this histogram and thereby determines the time of reception.
  • a rising or falling edge or a histogram portion or its center of gravity that is above a further detection threshold now applied to the histogram can be determined, or a functional, in particular parabolic, fit is carried out in the object peak 56.
  • the transmission time defined by the trigger pulse the light transit time and ultimately the distance of the object 16 are measured.
  • the elements 68, 70, 72, 74 and 76 are preferably part of the control and evaluation unit 22.
  • Figure 7 shows in the upper part the two transmission pulses 78 of two successive measurements.
  • the transmission pulses 78 can optionally also be interpreted as trigger pulses; both are related to one another with a known, constant time offset.
  • the adaptation pulse generation unit 70 generates adaptation pulses 80 associated with the trigger pulses, which are in the lower part of the Figure 7 are shown.
  • the temporal position shown here as a time offset ⁇ t, as well as Duration t D of the adaptation pulse can be specified.
  • Other parameters of the pulse characteristics are conceivable, such as amplitude or shape and duration of the rising or falling edge.
  • the adaptation pulse generation unit 70 can be implemented on a digital computing module or in integrated circuits, for example on an FPGA (Field Programmable Gate Array) or ASIC (Application-Specific Integrated Circuit). However, a simple analog circuit, which can be connected to such a digital component, is preferably sufficient, for example to provide the trigger pulse.
  • FPGA Field Programmable Gate Array
  • ASIC Application-Specific Integrated Circuit
  • FIG 8 shows an exemplary analog circuit for generating a positive adaptation pulse (U3, right) from a trigger pulse as a short positive input pulse (U1, left).
  • the trigger pulse charges a capacitor C1 via a diode D1, preferably a Schottky diode, and a resistor R1.
  • the capacitor voltage is divided down via a divider made up of two resistors R2 and R3.
  • the charging time constant C1 / (1 / (R1+Rdyn_D1) + 1 / (R2+R3)), with RDyn_D1 dynamic, current-dependent internal resistance of the diode D1 is chosen to be significantly shorter than the discharging time constant C1 * (R2 + R3).
  • the output level can be varied via the pulse width of the trigger pulse. With a very short trigger pulse, the charging is only incomplete and the voltage at C1 is reduced accordingly.
  • An adaptation pulse with the desired pulse characteristic can thus be generated by electrical control, namely a suitable trigger pulse, and/or the dimensioning of the switching elements.
  • Figure 9 shows an exemplary circuit for generating a negative adaptation pulse from a trigger pulse, which is now a negative pulse rising from a high potential at rest (active-low).
  • the capacitor C11 While the trigger pulse is present on the input side, the capacitor C11 is discharged via R11 and D11, with a discharge time constant C11 / (1 / (R11+Rdyn_D11) + 1 / R14 + 1 / (R12+R13)).
  • the capacitor C11 is charged back to the original U_C11 with the time constant C11 / (1 / R14 + 1 / (R12+R13)).

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Electromagnetism (AREA)
  • Optical Radar Systems And Details Thereof (AREA)
EP22175234.8A 2022-05-24 2022-05-24 Détection optique et mesure de distance Pending EP4283331A1 (fr)

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Citations (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6650404B1 (en) * 2002-05-28 2003-11-18 Analog Modules, Inc. Laser rangefinder receiver
US20050110976A1 (en) * 2003-11-26 2005-05-26 Labelle John Rangefinder with reduced noise receiver
EP1972961A2 (fr) 2007-03-22 2008-09-24 Sick Ag Capteur optoélectronique et procédé de mesure de l'éloignement ou de la modification de l'éloignement
EP2045625A1 (fr) 2000-05-31 2009-04-08 Sick Ag Procédé de mesure de distance et dispositif de mesure de distance
EP2182378A1 (fr) 2008-10-30 2010-05-05 Sick Ag Scanner laser mesurant l'éloignement
US8619239B2 (en) * 2011-01-28 2013-12-31 Analog Modules Inc. Accuracy of a laser rangefinder receiver
DE202013101039U1 (de) 2013-03-11 2014-03-12 Sick Ag Optoelektronischer Sensor zur Entfernungsmessung
DE102012021831A1 (de) * 2012-11-08 2014-05-08 Valeo Schalter Und Sensoren Gmbh Abtastende optoelektronische Detektionseinrichtung mit einer Detektionsschwelle, Kraftfahrzeg und entsprechendes Verfahren
DE102012021830A1 (de) * 2012-11-08 2014-05-08 Valeo Schalter Und Sensoren Gmbh Optoelektronische Detektionseinrichtung mit einstellbarer Biasspannung eines Avalanche-Photodetektors für ein Kraftfahrzeug, Kraftfahrzeug und entsprechendes Verfahren
EP3124996A1 (fr) * 2015-07-31 2017-02-01 Optex Co., Ltd. Circuit de retenue de détection erronée à télémètre laser
EP3270182A1 (fr) 2016-07-15 2018-01-17 Sick AG Capteur optoélectronique et procédé de détection d'objets dans une zone de surveillance
EP3518000A1 (fr) 2018-01-26 2019-07-31 Sick AG Capteur optoélectronique et procédé de détection d'objets
EP3557286B1 (fr) 2018-04-17 2020-04-15 Sick Ag Capteur optoélectronique et procédé de détection et de détermination de distance d'un objet
DE202019100793U1 (de) * 2019-02-12 2020-05-15 Sick Ag Optoelektronischer Sensor zur Erfassung von Objekten
EP3770633B1 (fr) 2019-07-23 2021-05-05 Sick Ag Capteur optoélectronique et procédé de détermination de distance
WO2021213013A1 (fr) * 2020-04-22 2021-10-28 上海禾赛科技股份有限公司 Circuit de détection à largeur d'impulsion de sortie réglable, unité de réception et radar laser

Patent Citations (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2045625A1 (fr) 2000-05-31 2009-04-08 Sick Ag Procédé de mesure de distance et dispositif de mesure de distance
US6650404B1 (en) * 2002-05-28 2003-11-18 Analog Modules, Inc. Laser rangefinder receiver
US20050110976A1 (en) * 2003-11-26 2005-05-26 Labelle John Rangefinder with reduced noise receiver
EP1972961A2 (fr) 2007-03-22 2008-09-24 Sick Ag Capteur optoélectronique et procédé de mesure de l'éloignement ou de la modification de l'éloignement
EP2182378A1 (fr) 2008-10-30 2010-05-05 Sick Ag Scanner laser mesurant l'éloignement
US8619239B2 (en) * 2011-01-28 2013-12-31 Analog Modules Inc. Accuracy of a laser rangefinder receiver
DE102012021830A1 (de) * 2012-11-08 2014-05-08 Valeo Schalter Und Sensoren Gmbh Optoelektronische Detektionseinrichtung mit einstellbarer Biasspannung eines Avalanche-Photodetektors für ein Kraftfahrzeug, Kraftfahrzeug und entsprechendes Verfahren
DE102012021831A1 (de) * 2012-11-08 2014-05-08 Valeo Schalter Und Sensoren Gmbh Abtastende optoelektronische Detektionseinrichtung mit einer Detektionsschwelle, Kraftfahrzeg und entsprechendes Verfahren
DE202013101039U1 (de) 2013-03-11 2014-03-12 Sick Ag Optoelektronischer Sensor zur Entfernungsmessung
EP3124996A1 (fr) * 2015-07-31 2017-02-01 Optex Co., Ltd. Circuit de retenue de détection erronée à télémètre laser
EP3270182A1 (fr) 2016-07-15 2018-01-17 Sick AG Capteur optoélectronique et procédé de détection d'objets dans une zone de surveillance
EP3518000A1 (fr) 2018-01-26 2019-07-31 Sick AG Capteur optoélectronique et procédé de détection d'objets
EP3557286B1 (fr) 2018-04-17 2020-04-15 Sick Ag Capteur optoélectronique et procédé de détection et de détermination de distance d'un objet
DE202019100793U1 (de) * 2019-02-12 2020-05-15 Sick Ag Optoelektronischer Sensor zur Erfassung von Objekten
EP3770633B1 (fr) 2019-07-23 2021-05-05 Sick Ag Capteur optoélectronique et procédé de détermination de distance
WO2021213013A1 (fr) * 2020-04-22 2021-10-28 上海禾赛科技股份有限公司 Circuit de détection à largeur d'impulsion de sortie réglable, unité de réception et radar laser

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